Fixing EJB Instantiation Issues In Tests

by Kenji Nakamura 41 views

Hey guys! Let's dive into a tricky issue we encountered in our SearchControllerDepartmentFilterRegressionTest and how we tackled it. This article will walk you through the problem, its impact, and the solution we implemented. So, buckle up and let's get started!

The Problem: Direct EJB Instantiation Causing NPEs

So, here's the deal. Our regression test, SearchControllerDepartmentFilterRegressionTest, was directly instantiating BillFacade (an EJB) in the setUp() method like this:

billFacade = new BillFacade();

Now, you might be thinking, "What's the big deal?" Well, the problem is that EJBs instantiated outside of a container context don't have their dependencies (like EntityManager) injected. This leads to those dreaded NullPointerExceptions (NPEs) when the tests are run. Imagine building a car but forgetting to install the engine – it’s just not going to work, right? That's precisely what was happening here. We were trying to run our tests with EJBs that weren't fully equipped, hence the NPEs.

Think of it like this: EJBs are designed to work within a special container that handles all the dependency injections and configurations. When you try to create an EJB instance directly using new BillFacade(), you're essentially bypassing this container. As a result, essential components like EntityManager, which are supposed to be injected by the container, are left uninitialized, leading to those pesky null pointers.

This issue is a classic example of why we need to be careful when working with enterprise Java components like EJBs in our tests. Directly instantiating them without the proper container support can lead to unpredictable behavior and make our tests unreliable. It's like trying to use a power tool without plugging it into a power source – it's just not going to work as expected. So, understanding how EJBs and their dependencies work within a container context is crucial for writing robust and reliable tests.

Impact: Flaky Tests and Unreliable Results

Now, let's talk about the impact of this issue. When we have tests that directly instantiate EJBs, things can get messy pretty quickly. Specifically, any test methods that call createIssueReport1() and createGrnTable() were failing with NPEs. This is a major headache because:

  • Our tests become flaky and unreliable. A test might pass one time and fail the next, making it hard to trust the results. It's like having a weather forecast that changes every five minutes – you can't really rely on it to plan your day.
  • Unit tests should be isolated and not depend on a container or database context. This principle ensures that tests are fast, predictable, and easy to debug. By directly instantiating EJBs, we were violating this principle and introducing external dependencies into our unit tests. It's like trying to build a house on a shaky foundation – the whole structure becomes unstable.

Flaky tests are the bane of any development team's existence. They erode confidence in the test suite and make it difficult to identify genuine issues. Imagine a scenario where your tests are constantly failing intermittently. You'd spend more time investigating false alarms than actually fixing real bugs. This not only slows down the development process but also increases the risk of shipping code with undetected errors.

Moreover, unit tests that depend on external contexts like containers or databases are inherently slower and more complex to set up. They also become more prone to failure due to issues in the external environment, such as database downtime or configuration errors. This defeats the purpose of unit testing, which is to provide rapid feedback on code changes in an isolated and controlled environment. Therefore, it's crucial to keep unit tests independent of external dependencies as much as possible.

Solution: Mocking EJBs with Mockito

Alright, so we've identified the problem and its impact. Now, let's get to the good stuff – the solution! To fix this, we decided to replace the direct EJB instantiation with Mockito mocks. If you're not familiar with Mockito, it's a fantastic mocking framework that allows us to create mock objects for testing purposes. Think of mocks as stand-ins for real objects, allowing us to control their behavior and verify interactions.

Here's what we did:

  1. Replace instantiation in setUp():

    We changed the code from:

    billFacade = new BillFacade();

    To:

    billFacade = org.mockito.Mockito.mock(BillFacade.class);

    This tells Mockito to create a mock object for BillFacade instead of trying to instantiate the real EJB.

  2. Add required imports:

    We added the following imports to our test class:

    import static org.mockito.Mockito.*;
import static org.mockito.ArgumentMatchers.*;

    These imports give us access to Mockito's mocking and argument matching capabilities.

  3. Add basic stubbing:

    We added some basic stubbing to define the behavior of the mock BillFacade:

    when(billFacade.findByJpql(anyString(), anyMap(), any())).thenReturn(new ArrayList<>());

    This tells Mockito that whenever the findByJpql method is called on the mock BillFacade, it should return an empty list. This is a simple example of stubbing, and we can add more complex stubbing as needed to simulate different scenarios in our tests.

    Mockito is a powerful tool for isolating our tests from external dependencies like EJBs. By using mocks, we can control the behavior of these dependencies and ensure that our tests focus on the logic of the code under test. It's like having a virtual playground where we can create any scenario we want without affecting the real world. This makes our tests more reliable, faster, and easier to maintain. Moreover, Mockito provides a rich set of features for verifying interactions with mocks, allowing us to ensure that our code is calling the dependencies correctly. This is crucial for catching subtle bugs that might otherwise slip through the cracks.

File Location: src/test/java/com/divudi/regression/SearchControllerDepartmentFilterRegressionTest.java (around line 36)

For those of you who want to dive into the code, you can find the affected file at src/test/java/com/divudi/regression/SearchControllerDepartmentFilterRegressionTest.java, specifically around line 36.

References: PR #15012 and Comment

If you're interested in the details of the fix, you can check out the following references:

These links will give you more context and insights into the discussion and implementation of the solution.

Key Takeaways

So, what have we learned from this adventure? Here are the key takeaways:

  • Avoid direct EJB instantiation in tests: Always use mocking frameworks like Mockito to create mock EJBs for testing.
  • Keep unit tests isolated: Unit tests should not depend on containers or databases.
  • Use mocks to control dependencies: Mocks allow you to define the behavior of dependencies and simulate different scenarios.
  • Mockito is your friend: Mockito is a powerful tool for writing robust and reliable tests.

By following these principles, we can ensure that our tests are fast, predictable, and easy to maintain. This not only improves the quality of our code but also makes our development process more efficient and enjoyable. Remember, writing good tests is an investment that pays off in the long run.

Conclusion

And that's a wrap, folks! We successfully tackled the EJB instantiation issue in our SearchControllerDepartmentFilterRegressionTest by using Mockito mocks. This not only fixed the NPEs but also made our tests more reliable and maintainable. Remember, testing is a crucial part of software development, and using the right tools and techniques can make all the difference. Keep coding, keep testing, and keep learning! Until next time, happy debugging!